R13 and R30 insulation would be what value?

[SuzukiGS750EZ]

Hey guys. Redid ceilings in the house and removed all old insulation. Had a ton of R13 on hand so put it up there for the time being. Its faced. Can I buy unfaced R30 and get a value of at least R38. My zone requires R38 to R49. Thanks!

 

[billconner]

Generally, for meeting code, you can just add them, so R43. If the batts are perpendicular to each other - without leaving gaps - slightly better performance.
Gaps, even as small as 1/8 to 1/4 inch, really hurt performance

 

[Firebrick43]

use it and cover with cellulose. It seals all the gaps. wont be as good as monolithic cellulose but if you already have it?

 

[pcmeiners]

For the rated r values added together, fiberglass would need to installed as per the manufacturers recommended guide. Basically your not going to have that optimal install. Fiberglass with any air flow through it gets a down rated R value. To get optimal R-value of what you plan you would need to follow Alliance member's use of cellulose as a cover. Unpacked as in attic install very little air permeates. Once cellulose settles in an attic basically there is no air flow through it.

 

[larry4406]

Please remove any Kraft paper between layers.

Kraft paper towards conditioned space; at least in my area.

 

[SuzukiGS750EZ]

Please remove any Kraft paper between layers.

Kraft paper towards conditioned space; at least in my area.

Yes, the insulation that’s currently in there is paper down. I was planning on using unfaced (no paper) fiberglass ontop of the already faced fiberglass.

 

[red]

If you're really ambitious, check your interior walls where they meet your ceiling joists. Seen plenty where the (wood) stud finishes drying out and pulls away from the sheetrock leaving a 1/8" to sometimes 1/4" inch gap, which allows air flow from your interior walls into your attic.
Foam in a can or caulk will close these gaps resulting in better R values. Another trick is to look where the old insulation was dirty . . . It's an easy way to find air leaks into your attic.

 

[hefnerconstructionlc]

As red said, air sealing I am convinced getting still air is more important than insulation. If the air is exchanged too rapidly, adding insulation has limited/much reduced benefits.

 

[Crazyjake8493]

As mentioned, air seal as best you can before you begin insulating. Insulation does very little if there's air passing through it.

Our second-floor ceiling joists were 2x6s so I put in R19 (face down) in the joist bays, and then unfaced R30 perpendicular to that with no gaps for an R49 total (minimum in this area). I made sure to air seal any electrical box/wire penetrations, open tops of stud bays, and the infamously difficult to insulate space behind our knee walls.

 

[NUTTSGT]

Yes, the insulation that’s currently in there is paper down. I was planning on using unfaced (no paper) fiberglass ontop of the already faced fiberglass.

I did a blanket layer in our attic over the old blown cellulose. One layer of R13, with another layer 90° perpendicular to the first.

It did make a difference and pretty sure it paid for most of itself the first winter.